The known methods and arrangements for monitoring trafficways are generally distinguished by the use of different types of sensors which are either embedded in the pavement of the roadway (invasive sensors) or are arranged above the roadway (noninvasive sensors). Invasive sensors require a high outlay for installation and must be exchanged from time to time depending on the wear of the roadway pavement. Moreover, they are not suitable for stationary arrangements. The trafficway monitored by them is limited by the arrangement of the embedded sensors.
In EP 2 048 515 A1, instead of embedding a sensor at a predetermined location in each individual lane of the multiple-lane roadway, a radar beam is directed substantially horizontal to the roadway and along the edge of the roadway across all of the lanes of the roadway. For this purpose, an angle-resolving radar device (FMCW radar device) for transmitting and receiving radar radiation is positioned relative to the roadway such that it transmits a radar beam forming a radar lobe with an aperture angle of 20° to 40° at a horizontal mounting angle of the radar beam axis (line of symmetry of the radar lobe) relative to the roadway edge of less than 45°. The radar device can be arranged in such a way that when driving through the radar lobe the vehicles drive toward the radar device (oncoming traffic, front-measuring radar device) or away from the radar device (receding traffic, rear end-measuring radar device). In so doing, the monitored trafficway is determined with respect to its position and size by the position of the radar beam axis and the aperture angle of the radar lobe.
According to EP 2 048 515 A1, cited above, the changing relative position of the vehicle with respect to the radar device over the measurement duration is derived from the radar signals reflected by a vehicle as it drives through the radar lobe. When the relative position of the stop line to the radar device is known, the relative position of the vehicle to the radar device can be used to determine its perpendicular distance from the stop line. Subsequently, the time point at which the stop line is passed can be deduced from the vehicle speed in question which has also been derived and from its perpendicular distance from the stop line, and a photograph is taken if this time point does not occur within the green-light phase of a traffic signal installation associated with the stop line.
The position of the vehicle associated with every measurement time is defined here by the position of a so-called point of impingement for which a distance and an angle are determined from the reflection signals.
For oncoming traffic for which only the front end of the vehicle lies in the reflection region of the radar beam with increasing proximity to the stop line, the aforementioned method allows a reliable detection of traffic violations at a traffic signal installation, since the front end of the vehicle, which is naturally the first to pass the stop line, substantially determines the position of the so-called point of impingement.
For receding traffic for which only the rear end of the vehicle lies in the reflection region of the radar beam with increasing proximity to the stop line and the rear end of the vehicle accordingly substantially determines the position of the so-called point of impingement, there is no detection of traffic violations in which the front end of the vehicle but not the rear end of the vehicle passes the stop line at a point in time depending on a given switching state of the traffic signal installation.
A method is known from the not prior published DE 10 2012 107 444 B3 in which vehicles are measured multiple times while driving through a radar lobe and specific position values are formed so as to be associated with measurement times. A specific position value can be a specific radial distance or a specific object angle. The change in the specific position value over time is examined over the length of a segment for the occurrence of a discontinuity. The length of the segment depends upon the length of the vehicle and makes classification possible.